Mills told NFIB members that the Affordable Care Act is preventing small and medium business expansion in Minnesota, and he would vote to repeal the law if elected.

"At the end of the day, it is our tax policy that has put a target on the back of our small and medium business people and their employees," Mills said. "We need a flatter, fairer tax system that will allow economic activity and job growth."

Meanwhile, Nolan is criticizing Mills for a campaign contribution he accepted in late June.

According to the Federal Election Commission, the employee funded Koch Industries Inc. PAC contributed $2,500 to the Mills campaign.

The Nolan campaign slammed Mills' contribution from the political action committee.

"Stewart Mills finds it "personally offensive" to suggest that millionaires like him should pay their fair share, but he will happily take thousands of dollars from the billionaire Koch brothers," Kendal Killian, Nolan's campaign manager said Thursday.

"Mills' only goal is to help millionaires and billionaires get richer," Killian added. "If elected, he would side with the super rich and not with middle-class Minnesotans."

A Mills spokeswoman fired back.

"People are tired of Rick Nolan, who would rather raise money with convicted child molester Peter Yarrow, vote against our 2nd amendment rights, and side with Barack Obama and Nancy Pelosi instead of representing the values of our part of Minnesota," Chloe Rockow, Mills' communication director said.

Campaign cash linked to Koch Industries has sparked debate on the influence donors have on politicians in recent election cycles.